The present invention relates to an electric heat sealer, and more particularly to an electric heat sealer which can be controlled to break the electric circuit when the apparatus is not in use, so as to prevent an electric connection by a false action.
A variety of electric heat sealers have been developed for home use, and have appeared on the market. An example of such a device is disclosed in U.S. Pat. No. 5,142,123.
Conventional electric heat sealers are functional for sealing plastic bags and the like. However, these electric heat sealers have no safety control means. When an electric heat sealer is touched by an external force, the sealing mechanism may be electrically connected to produce heat, potentially causing an accident to occur.
A need exists for an electric heat sealer which eliminates the aforesaid problem, and which is handy and safe in use.
In accordance with one aspect of the present invention, there is provided an electric heat sealer comprising a casing, a battery chamber, a spring holder, a sealing mechanism, a press bar, and a safety device. The casing holds the battery chamber, the spring holder, the sealing mechanism and the safety device on the inside. The battery chamber comprises a front upright support; a rear upright support; a first front terminal plate and a second front terminal plate respectively mounted on the front upright support; a pair of rear terminal plates respectively mounted on the rear upright support; a first metal contact plate mounted on the front upright support and connected the first front terminal plate; and a second metal contact plate mounted on the front upright support and spaced from the second terminal plate by a gap. The second terminal plate is forced into contact with the second metal contact plate when a battery set is installed in the battery chamber. The spring holder is mounted in the casing and spaced between the first metal contact plate and the second metal contact plate. The sealing mechanism is mounted in the casing and moved up and down relative to the first and second metal contact plates.
The sealing mechanism comprises a heat insulative base; an electric wire; two metal locating plates; and a compression spring. The heat insulative base comprises a protrusive middle portion. The electric heating wire is mounted on the protrusive middle portion of the heat insulative base. The metal locating plates are fixedly fastened to the heat insulative base at two opposite sides and respectively connected to two opposite ends of the electric heating wire. The compression spring is connected between the spring holder and the protrusive middle position of the heat insulative base.
The press bar has a fixed end pivotally connected to one end of the casing and a free and fixedly mounted with a heat insulative press block. The heat insulative press block is forced against the protrusive middle portion of the heat insulative base of the sealing mechanism when the press bar is depressed.
The safety device comprises a safety switch with two opposite terminals. The safety switch has two lead wires respectively extended from the two opposite terminals thereof and respectively connected to the second terminal plate and the second metal contact plate.
In a preferred embodiment, the inventive electric heat sealer further includes a protective frame pivotally connected to the casing and pivotable between a first position and a second position. In the first position, the protective frame is spaced between the heat insulative base of the sealing mechanism and the heat insulative press block of the press bar. In the second position, the protective frame is pivoted out of the space between the base and the press block.
Preferably, the electric heat sealing wire and the press block are covered by heat insulative sheets, which preferably are comprised of a heat-resistant material such as a Teflon mesh.
In another preferred embodiment, the inventive heat sealer further includes a cover device for the casing. The cover device has defined therein an opening through which the protrusive middle portion of the heat insulative base of the sealing mechanism extends out of the casing. More specifically, the cover device includes a front cover plate disposed on a front portion of the casing, a rear cover plate disposed on a rear portion of the casing, and an intermediate cover plate disposed on a middle portion of the casing over the battery chamber.
In accordance with another aspect of the present invention, there is provided an electric heat sealer which includes a casing; a cover device; first and second metal contact plates; a sealing mechanism; resilient means, such as a spring, piston or the like, biasing the sealing mechanism in an upward direction; operating means pivotally connected to the casing; and a safety device.
The cover device covers the casing and has an opening formed therethrough. The first and second metal contact plates are mounted within the casing below the opening in the cover device. The sealing mechanism is mounted in the casing and moves up and down relative to the first and second metal contact plates. The sealing mechanism includes: a heat insulative base having a protrusive middle portion; an electric heating wire mounted on the protrusive middle portion of the heat insulative base, the electric heating wire having two opposite ends; and two metal locating plates mounted on the heat insulative base and respectively connected to the opposite ends of the electric heating wire.
The resilient means biases the sealing mechanism in an upward direction so that the protrusive middle portion of the heat insulative base extends through the opening in the cover device. The operating means is pivotally connected to the casing and extends above the opening in the cover device. The operating means is movable downwardly to engage an object to be sealed which is supported on the protrusive middle portion of the heat insulative base extending through the opening and urge the heat insulative base downwardly and cause the metal locating plates to engage the metal contact plates. This causes electrical current to flow through and heat the electric heating wire when the metal contact plates are connected to a source of electrical current.
The safety device selectively prevents electrical current from flowing through the electric heating wire.
In a preferred embodiment, the inventive heat sealer is adapted to be supplied with electrical current from at least one current source selected from the group consisting of a DC current source and an AC current source. Particularly, the inventive heat sealer is adapted to be supplied with electrical current from both a DC current source and an AC current source.
More particularly, the inventive heat sealer is adapted to be supplied with electrical current from a DC current source which is a battery set. In this embodiment, the casing defines a battery chamber adapted to receive a battery set, the battery chamber including a front upright support; a rear upright support; first and second front terminal plates respectively mounted on the front upright support; a pair of rear terminal plates respectively mounted on the rear upright support; a first metal contact plate mounted on the front upright support and connected to the first front terminal plate; and a second metal contact plate mounted on the front upright support and spaced from the second terminal plate by a gap. The second terminal plate is forced into contact with the second metal contact plate when a battery set is installed in the battery chamber.
Preferably, the safety device includes a safety switch having two opposite terminals and two lead wires respectively extending from the two opposite terminals thereof and respectively connected to the foregoing second terminal plate and the second metal contact plate.
In accordance with a further aspect of the present invention, there is provided an electric heat sealer comprising: a casing having an opening formed therethrough; first and second metal contact plates mounted within the casing below the opening; a sealing mechanism as described above, the sealing mechanism being mounted in the casing and moving up and down relative to the first and second metal contact plates; resilient means biasing the sealing mechanism in an upward direction so that the protrusive middle portion of the heat insulative base extends through the opening in the casing; operating means pivotally connected to the casing and extending above the opening in the casing as described above; and a safety device which selectively prevents electrical current from flowing through the electric heating wire.
Other objects, features and advantages of the present invention will become apparent to those skilled in the art from the following detailed description. It is to be understood, however, that the detailed description and specific examples, while indicating preferred embodiments of the present invention, are given by way of illustration and not limitation. Many changes and modifications within the scope of the present invention may be made without departing from the spirit thereof, and the invention includes all such modifications.